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White Balancing Questions

Hi, I just recently picked up a Godox QS400 for my studio. Previously I was using just speedlights for all my off camera flash portraits. I soon realised that leaving my camera settings on "Flash" white balance gave less than accurate colour rendition. I decided to do the PRE Preset manual white balance from a photograph of a white sheet of paper.

My question is this, do I have to make a manual white balance every time I move the strobe into a different positions or can I just leave it on the one preset photo taken?. Also what if I change the light modifier to a different softbox or increase/decrease the strobe power?

If the Godox is the only light source, then once you've made a PRE whitebalance check you're good to go for the rest of eternity using just that single PRE setting.
Of course light sources should vary over time, but I doubt it'd make all that much difference as the light temperature changes(if it does!) over time.

But, if any other ambient lighting sources are present, then obviously you'd need to do WB presets every time the external ambient lighting changes .. or for every shoot.

So lets say you have a few fluoro lights in a studio as well as the Godox .. but no external sunlight entering the studio.
Your PRE WB setting should be good if you had those fluoros on during the WB preset.
But if you change any of the fluoros(eg. they die) .. then you'd have to redo the WB preset.
Similarly, if you have any outside light, or any other variable light sources entering into the lighting mix .. obviously you'd have to do a WB PRE every time.

I can say for sure if you'd have to redo a WB preset for varying power levels .. I have no experience at all .. but if the varied power emanates from the one light tube, then you would assume that light tube should provide fairly constant light quality/colour no matter how much power it's putting out.
But if the light source relies on multiple light tubes for varying power, then you'd have to take that into account and do some checks.
(I don't know what a Godox QS400 is, so no idea on it's inner workings).

I reckon that in a technical sense, a light modifier should make a difference to light colour quality. If you had the time to test that I'd recommend that you do so. But in saying that, I doubt anyone could see with the naked eye any actual difference.
So I'd reckon(using guessing/theory) that it wouldn't make an observable difference.
If you measured a professional standard grey card tho, it would probably register a very slight difference between a modifier on or off.
Obviously if you used a light modifier that is visibly coloured in any way, you'd do a WB check and an extreme example of that would be if the light modifier was say red or blue .. obviously the resultant light would be red or blue. So think of it in terms of degrees of difference in light output. If it doesn't lok obviously coloured in any way, it probably won't make all that much difference .. using the same light source that is.

The reason you see differences in WB settings between speedlights and the Godox is simply that the light source is different.

I'm certainly no expert on the subject, but here is my approach.
Instead of using custom white balances for every lighting set up or modification, would the purchase of the X-rite ColorChecker Passport be an option?
I purchased one a few years ago, then set up a database set of shots in Lightroom for different lighting situations (colour callibration profiles within Lightroom) eg: Perth sunny, Perth Cloudy, Studio lights, Speedlite etc.
On every shoot, no matter whether its indoors or outdoors, I take my first shot of the ColorChecker Passport. When processing the shoot I choose the appropriate colour callibration profile within Lightroom, and then white balance off one of the grey squares on the shot of the ColorChecker passport. I then sync the rest of the shots with that profile and white balance.
Hope that makes sense.